This research will better define the control of renin release from the canine kidney and will emphasize the negative feedback mechanisms. Work completed in the one-kidney, one clip, Goldblatt hypertensive dog will be extended to the two kidney, one clip reno-vascular hypertensive dog. 1) It will be determined if the intrarenal angiotensin II-sodium interdependent negative feedback mechanism is similar in the two kidney and one kidney dog. Aortic blood pressure and plasma renin activity will be followed in the two kidney dog and compared with the one kidney dog. 2) Renal denervated dogs will be studied to determine if the renal nerves are necessary for the short loop negative feedback mechanism on renin release. 3) The relationship between the renal prostaglandins and the angiotensin II-sodium renal vasoconstrictive mechanism and negative feedback on renin release will be studied in conscious one-kidney one clip Goldblatt hypertensive dog. The angiotensin II-sodium interdependent vasoconstrictive mechanism will be studied in patients with renal artery stenosis in order to determine if this negative feedback mechanism determines whether hypertension develops and its severity in patients with renal artery stenosis. The role of this mechanism in determining peripheral resistance in patients with renal artery stenosis and essential hypertension with different levels of plasma renin activity. The peripheral resistance will be studied by measuring cardiac output, limb blood flow with plethysmography before and after chronic converting enzyme inhibition with SO 14225.